Process of rosin sizing paper



United States Patent US. Cl. 162180 6 Claims ABSTRACT OF THE DISCLOSUREA process of sizing paper in which a water-soluble aluminate is added toaqueous 'wood pulp until its pH is at least 9, a material yieldinghydrogen ions and nonaluminum-containing polyvalent anions is added tobring the pH down to not less than about 4.5, and rosin size is appliedto the surface of paper made from the pulp.

This invention relates to the sizing of paper and to a novel method ofincreasing the resistance of paper to water penetration and otherwiseenhancing the quality of the sizing of the paper.

This application is a continuation of SN. 716,001, filed Mar. 26, 1968now abandoned and a continuationin-part of co-pending U.S. Ser. No.549,819, filed May 13, 1966, now abandoned.

US. Pat. No. 3,074,843 issued to Lagally et al. shows a process ofproducing paper having high dry strength and good wet strength whereinaluminum hydroxide is precipitated by mixing an aluminum-containingcompound and an acid, a base, or an aluminum salt in the absence ofnonaluminum-containing polyvalent anions (e.g., the sulfate ion).Optimum results were achieved at a pH within the range of 6 to 9. See,particularly, column 6, lines 29 to 32, and column 2, lines 61 to 63, ofthe Lagally et al. patent. Lagally et al. stress their need to be freeof nonaluminum-containing polyvalent anions by calling it essential totheir invention. See column 2, lines 27 and 28, of the Lagally et al.patent.

It has now been found, however, that the stated need of Lagally et al.for the attainment of strength when wet can be obviated, and thatremarkable levels of sizing can be obtained concurrently with thedevelopment of strength. It has been found that, if a water-solublealuminate is added to an aqueous wood pulp slurry until its pH is atleast 9, i.e., 9 or above and if a material yielding hydrogen ions suchas sulfuric acid or papermakers alum is then added to the pulp andaluminate mixture to bring the overall pH down, i.e., to bring the pHdown to not less than about 4.5, aluminum hydroxide will precipitate insuch a manner and to such a degree as to assure excellent levels ofsizing once rosin size or the like is added to complete the process. Inshort, then, it has been found that, if the pH of the wood pulp isattended to correctly, the presence of the nonaluminumcontainingpolyvalent anions of papermakers alum Al (SO .14H Oor sulfuric acid isof little or no deleterious effect. The following examples, whichdescribe a standard sizing method ,(Example 1) and variations of themethod of present invention (Examples 2 to 18), and tables, whichcompile data of tests made on products of the examples, confirm thisfinding:

EXAMPLE 1 A mixture of 60% and 40% hardwood kraft pulp, bleached to 85%GE. brightness, was refined in an Patented Nov. 17, 1970 experimentalbeater, at 1.75% consistency, to 509 CS. freeness. Forty grams (ovendrybasis) of the refined pulp were suspended in distilled water at 3%consistency. Fortified size (commercially available Paper Product 2409)was added to the slurry at a rate of 42.8 pounds of size solids per tonof pulp. A mechanical stirrer was used to keep the slurry thoroughlymixed during the addition. Stirring was continued, and after fiveminutes papermakers alum 'was added at the rate of 53.5 pounds Al (SO.14H O per ton of pulp. Stirring was continued for 10 minutes. pH of theslurry after the addition of alum was 4.0. A solution of half normalsodium hydroxide was added to pH 5.0. Stirring was continued for oneminute. Consistency was adjusted to 0.375% with water containing enoughhydrochloric acid to give pH 5.0. Handsheets were formed on a Britishsheet mold, pressed between a polished metal plate and blotters, clampedin rings, and dried in a forced-draft oven at 150 C. for 30 minutes.Basis weight and caliper averaged pounds and 7.0 mils, respectively.Before testing, sheets were brought into equilibrium with the atmosphereof a room maintained at 50% relative humidity and 73 F.

EXAMPLE 2 Thirty grams (ovendry basis) of the refined pulp used inExperiment 1 were adjusted to 3% consistency with distilled water. Asolution of sodium aluminate (commercially available Nalco 680) wasslowly added to the slurry at the rate of 90 pounds per ton of pulp.Stirring was rapid during this addition. After five minutes ofcontinuous stirring, the slurry was transferred to a TAPPI standarddisintegrator. The disintegrator was started, and as violent agitationbegan pH was adjusted to 5.5 by the addition of a normal solution ofsulfuric acid. At this point, flocculation occurred. Cf., Curtman, L.J.; Qualitative Chemical Analysis; The MacMillan Company; New York,1938; p. 181 and Kolthoff et al.; Textbook of Quantitative InorganicAnalysis (3rd ed.); The MacMillan Company; New York, 1952, p. 318. Theslurry was returned to a beaker and stirring was continued for 25minutes, during which period a solution of fortified rosin size (PaperProduct 2409) was delivered into the mixture at the rate of 3.4 poundsof size solids per ton of pulp. The slurry was diluted to 0.375%consistency, and handsheets were prepared, pressed, and conditioned asin Experiment 1.

Each dried sheet was weighed, dipped in a solution of fortified rosinsize (Paper Product 2409), blotted lightly, weighed, and heated toincipient dryness at C. between a polished metal plate and blotters on aCarver press. The sized sheets were clamped in rings and dried in aforced-draft oven at 105 C. for 30 minutes. Size solids pickup wasequivalent to 3.4 pounds per ton of pulp.

EXAMPLE 3 Example 2 was repeated, except that the slurry of pulp andsodium aluminate was adjusted to pH 5 .5 by the addition of a solutionof papermakers alum.

EXAMPLE 4 Thirty grams (ovendry basis) of the pulp used in Experiment 1were suspended in distilled water at 3% consistency. A solution ofsodium aluminate was slowly added to the slurry at the rate of 90 poundsNa Al O .3H O per ton of pulp. Stirring was rapid during this addition.The mixture was transferred to a TAPPI standard disintegrator, and asviolent agitation began, a normal solution of sulfuric acid was rapidlyadded to the slurry in such volume as to lower pH to 5.5 andflocculation of the variety discussed in the Curtman and Kolthofl et a1.texts, supra, occurred. Agitation was continued for 30 seconds. Thetreated pulp was returned to a beaker and stirred at a moderate rate for20 minutes. Handsheets were prepared, pressed, and dried as inExperiment 1. Each dried sheet was weighed, dipped in a fresh solutionof fortified rosin size (Paper Product 2409), blotted ligthly, weighed,and heated to incipient dryness at 105 C. between a polished metal plateand blotters on a Carver press. The sized sheets were clamped in ringsand dried in a forced-draft oven at 105 C. for 30 minutes. Basis weightand caliper averaged 100 pounds and 7.0 mils, respectively. Size solidpickup was equivalent to 6.8 pounds per ton of pulp.

EXAMPLE Example 4 Was repeated, except that pH of the slurry of pulp andsodium aluminate was adjusted to 5.5 by the addition of a solution ofpapermakers alum.

EXAMPLE 6 Thirty grams (ovendry basis) of the pulp used in Experiment lwere suspended in distilled water at 3% consistency. A solution ofsodium aluminate was slowly added to the slurry at the rate of 90 poundsNa Al O -3H O per ton of pulp. Stirring was rapid during this addition.While stirring continued, 0.5 N sulfuric acid was slowly added in suchvolume as to lower pH to 5.5 and flocculation of the variety discussedin the Curtman and Kolthoif et a1. texts, supra, occurred. Agitation wascontinued for 20 minutes. Handsheets were prepared, pressed, and driedas in Experiment 1. Each dried sheet was weighed, dipped in a freshsolution of fortified rosin size (Paper Product 2409), blotted lightly,weighed, and heated to incipient dryness at 105 C. between polishedmetal plates and blotters on a Carver press. The sized sheets wereclamped in rings and dried in a forced-draft oven at 105 C. for 30minutes. Basis Weight and caliper averaged 100 pounds and 7.0 mils,respectively. Size solids pickup was equivalent to 6.8 pounds per ton ofpulp.

EXAMPLE 7 Example 6 was repeated, except that pH of the slurry of pulpand sodium aluminate was adjusted to 5.5 by the addition of a solutionof papermakers alum.

EXAMPLE 8 Example 6 was repeated, except that sodium aluminate was usedat the rate of 60 pounds per ton of pulp, and that size solids pickupwas equivalent to pounds per ton of pulp.

EXAMPLE 9 Example 8 was repeated, except that pH of the slurry of pulpand sodium aluminate was adjusted to 5 .5 by the addition of a solutionof papermakers alum.

EXAMPLE l0 and Koltholf et al. texts, supra, occurred. Violent agitation was continued for 30 seconds; the treated pulp was returned to abeaker and stirred at a moderate rate for minutes. Handsheets wereprepared, pressed, and dried as in Experiment 1. Each dried sheet wasweighed, dipped in a fresh solution of pale rosin size (Paper Product2408A), blotted lightly, weighed, and heated to incipient 4 dryness at105 C. between a polished metal plate and blotters on a Carver press.The sized sheets were clamped in rings and dried in a forced-draft ovenat 105 C. for 30 minutes. Basis weight and caliper averaged 100 poundsand 7.0 mils respectively. Size solids pickup was equivalent to 5.7pounds per ton of pulp.

EXAMPLE 11 Example 10 was repeated, except that pH of the slurry of pulpand sodium aluminate was adjusted to 5.5 by the addition of a solutionof papermakers alum.

EXAMPLE 12 Example 4 was repeated, except that the pulp was unbleachedpine kraft, and that pH of the slurry of pulp and sodium aluminate wasadjusted to 5.5 by the addition of 0.5 N sulfuric acid.

EXAMPLE 13 Example 12 was repeated, except that pH of the slurry of pulpand sodium aluminate was adjusted to 5.5 by th addition of a solution ofpapermakers alum.

EXAMPLE 14 Four hundred thirty grams of pulp (ovendry basis) similar tothat used in Experiment 1 were Weighed into a Valley beater and dilutedto 1.75% consistency with demineralized water. A solution of sodiumaluminate containing the equivalent of pounds Na Al O -3H O per ton ofpulp was added to the slurry during mixing. A 0.5 N solution of sulfuricacid was added to adjust pH to 5.5. Here, flocculation as discussed inthe Curtman and Kolthoff et al. texts, supra, occurred. Mixing wascontinued for 20 minutes after the addition of acid before refining wasbegun. With a 5-kilogram weight in place, the pulp was beaten for 21minutes to 509 CS. freeness. The refined pulp was transferred to a largecontainer and diluted with demineralized Water (at pH 5.5) tos'heetmaking consistency. Handsheets were prepared, pressed, dried,sized, and conditioned as in Experiment 4.

EXAMPLE 15 Example 8 was repeated, except that a solution of sodiumaluminate containing the equivalent of 40' pounds Na Al O -3H O per tonof pulp was added to the slurry during mixing.

EXAMPLE 16 Example 15 was repeated, except that pH of the slurry of pulpand sodium aluminate was adjusted to 5 .5 by the addition of a solutionof papermakers alum.

EXAMPLE 17 Example 15 was repeated, except that pH of the slurry of pulpand sodium aluminate was adjusted to 6.5 by the addition of a 0.5 Nsolution of sulfuric acid.

EXAMPLE 18 Example 17 was repeated, except that pH of the slurry of pulpand sodium aluminate was adjusted to 4.5 by the addition of a 0.5 Nsolution of sulfuric acid.

EXAMPLE l9 Thirty grams (ovendry basis) of bleached kraft pulp at C8.freeness 500 were suspended in distilled Water at 3% consistency. Asolution of sodium aluminate was slowly added to the slurry at the rateof 90 pounds Na Al O 3H O per ton of pulp. Stirring was rapid duringthis addition. While stirring continued, a normal solution oforthophosphoric acid was slowly added in such volume as to lower pH to5.4 and flocculation of the variety discussed in the Curtman andKolthofi et al. texts, supra, occurred. Agitation was continued for 20minutes. Handsheets Were prepared, pressed, and dried as inExperiment 1. Each dried sheet was weighed, dipped in a fresh solutionof fortified rosin size (Paper Product 2409), blotted lightly, weighed,and heated to incipient dryness at 105 C. between polished metal platesand blotters on a Carver press. The sized sheets were clamped in ringsand dried in a forced-draft oven at 105 C. for 30 minutes. Basis weightand caliper averaged 100 pounds and 7.0 mils, respectively. Size solidspickup was equivalent to 6.8 pounds per ton of pulp.

EXAMPLE 20 Forty grams (ovendry basis) of refined pulp similar to thatused in Example 1 were suspended in distilled water at 3% consistency.Slurry pH was adjusted to 1.9 by the slow addition of a normal solutionof sulfuric acid. Stirring was rapid during this addition. After fiveminutes of continuous stirring, the slurry was transferred to a TAPPIstandard disintegrator. The disintegrator was started, and as violentagitation began pH was adjusted to 5.5 by the addition of a solution ofsodium aluminate at the rate of 90 pounds per ton of pulp. Flocculationoccurred.

The slurry was returned to a beaker and stirring was continued for 25minutes, during which period a solution of fortified rosin size wasdelivered into the mixture at the rate of 3.4 pounds of size solids perton of pulp. The slurry was diluted to 0.375% consistency, andhandsheets were prepared, pressed, and conditioned as in Example 1.

Each dried sheet was weighed, dipped in a solution of fortified rosinsize, blotted lightly, weighed, and heated to incipient dryness at 105C. between a polished metal plate and blotters on a Pasadena press. Thesized sheets were clamped in rings and dried in a forced-draft oven at105 C. for 30 minutes. Size solids pickup was equivalent to 3.4 poundsper ton of pulp.

EXAMPLE 21 Forty grams (ovendry basis) of pulp similar to that used inExample 1 were suspended in distilled water at 3% consistency. Slurry pHwas adjusted to 1.9 by the addition of a normal solution of sulfuricacid. Stirring was rapid after this addition. The mixture was transferred to a TAPPI standard disintegrator and as violent agitation begana solution of sodium aluminate was added in such volume as to lower pHto 5.5. Flocculation occurred.

Agitation was continued for 30 seconds. The treated pulp was returned toa beaker and stirred at a moderate rate for 20 minutes. Handsheets wereprepared, pressed, and dried as in Example 1. Each dried sheet wasweighed, dipped in a fresh solution of fortified rosin size, blottedlightly, weighed, and heated to incipient dryness at 105 C. between apolished metal plate and blotters on a Pasadena press. The sized sheetswere clamped in rings and dried in a forced-draft oven at 105 C. for 30minutes. Basis weight and caliper averaged 100 pounds and 7.0 mils,respectively. Size solids pickup was equivalent to 6.8 pounds per ton ofpulp.

EXAMPLE 22 Example 21 was repeated, except that pH of the pulp slurrywas adjusted to 3.7 by the addition of a solution of papermakers alumbefore adding a solution of sodium aluminate to flocculation pH 5.5.

EXAMPLE 23 Forty grams (ovendry basis) of pulp similar to that used inExample 1 were suspended in distilled water at 3% consistency. While theslurry was slowly stirred, pH was adjusted to 1.9 by the slow additionof half normal sulfuric acid. After 5 minutes pH was adjusted to 5.5 bythe addition of a solution of sodium aluminate containing the equivalentof 90 pounds Na Al O .3H O per ton of pulp. Agitation was continued for20 minutes. Handsheets were prepared, pressed, and dried as inExample 1. Each dried sheet was weighed, dipped in a fresh solution offortified rosin size, blotted lightly, weighed, and heated to incipientdryness at C. between polished metal plates and blotters on a Pasadenapress. The sized sheets were clamped in rings and dried in aforced-draft oven at 105 C. for 30 minutes. Basis weight and caliperaverage 100 pounds and 7.0 mils, respectively. Size solids pickup wasequivalent to 6.8 pounds per ton of pulp.

EXAMPLE 24 Example 23 was repeated, except that sulfuric acid was addedto the pulp slurry in such amount that flocculation pH 5.5 was attainedby the addition of the equivalent of 60 pounds Na Al O 3H O per ton ofpulp.

EXAMPLE 25 Example 24 was repeated, except that the volume of sulfuricacid used to adjust slurry pH was such as to require only 40 pounds NaAl O .3H O per ton of pulp to give flocculation pH 5.5.

TABLE 1 Lactic acid Cofiee Dry Water penepeneindi- Cobb absorpscope,scope, cator, size, g./ tion, minutes minutes seconds sq. m. percent Thedata set forth in Table I, supra, suggest that a unique and remarkablyeffective method of sizing paper has been developed. Sizing by thepresent flocculated aluminate-rosin size procedure has producedhandsheets superior in the characteristics evaluated to similar sheetsprepared by orthodox means.

The following additional observations are worthy of note:

Variations in flocculation pH between 4.5 and 6.5 have little influenceon sizing (Examples 15, 17, and 18, Table I);

Violent agitation during and immediately after flocculation does notappear to affect sizing (Examples 4 and 6, Table I); and

Both fortified rosin size and regular pale rosin size are compatiblewith the flocculated aluminate system (Examples 2 and 10, Table I).

What is claimed is:

1. A process for sizing paper made from wood pulp comprising a step ofadding a water-soluble aluminate to an aqueous slurry of wood pulp in anamount sufficient to bring the pH of the aqueous slurry of the wood pulpto about 9 and above, a step of adding a material yielding hydrogen ionsand non-aluminum-containing polyvalent anions to the aqueous slurry ofwood pulp in an amount sufficient to flocculate the aluminate withoutlowering the pH of the aqueous slurry of the wood pulp beyond about 4.5,and a step of adding a rosin size to the wood pulp after it istransformed from the aqueous slurry into a web of paper.

2. A process for sizing paper made from wood pulp comprising a firststep of adding a water-soluble aluminate to an aqueous slurry of woodpulp in an amount sufficient to bring the pH of the aqueous slurry ofwood pulp to about 9 and above, a second step of adding a materialyielding hydrogen ions and non-aluminum-containing polyvalent anions tothe aqueous slurry of wood pulp in an amount suflicient to flocculatethe aluminate without lowering the pH of the aqueous slurry of the woodpulp beyond about 4.5, and a third step of adding a rosin size to thewood pulp after it is transformed from the aqueuos slurry into a web ofpaper.

3. The process of claim 1 wherein the Water-soluble aluminate is sodiumaluminate.

4. The process of claim 1 wherein the material is sulfuric acid.

5. The process of claim 1 wherein the material is paper- 15 makers alum.

References Cited UNITED STATES PATENTS 4/1919 De Cew 16218O 1/1969 Jones162185 S. LEON BASHORE, Primary Examiner R. H. ANDERSON, AssistantExaminer US. Cl. X.R.

